A cobpobation of



Apr. 17, 1923.

A. E@ KEITH TELEPHONE TRUNKING SYSTEM 9v Sheets-Sheet l Original Filed May 21 15.307

9 Sheets-Sheet 2 Apr. 17, 1923,

A. E. KEITH TELEPHONE TRUNKING SYlSTEM Original Filed May 2l 190'? Apr. 17, 1923. 1,451,912

. A. E. KEITHv TELEPHONE TRUNKING SYSTEM Original Filed May 21, 190'? 9 Sheets-Sheet 5 A. E. KEITH' TELEPHONE TRUNKING SYSTEM Apr. 17., 1923.

Originafl Filed May 2l 1907 9 Sheets-Sheet 4 Apr, 17, 1923.

A. E. KEITH TELEPHONE TRUNKING SYSTEM Original Filed May 21, 190'? 9 Sheets-Sheet 5 M JEU )RH JQ Apr. 17, 1923. 1,451,912

A. E. KEITH TELEPHONE TRUNKING SYSTEM Original Filed May 21, 190'? 9 Sheetvs-Sheet 6 OOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOCOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOOO zal OOOOOOOOOOOOOOOOOOOOOOOO O OOOOOOOOOOOOOOOOOOOOOOOOO 4Il N OOOOO OOOQOOOOOOOOOOOOO OOO OOOOOOOOOOOOOOOOOOOOOOOOO Apr. 17, 1923'.

A. E. KEITH TELEPHONE TRUNKING SYSTEM Original Filed May 2l 1907 9 Sheets-Sheet 7 Apr. 17, 1923. 1,451,912

A. E. KEITH TELEPHONE TRUNKING SYSTEM Original Filed May 21, 1907 9 Sheets-Sheet 9 Q. W .d zcyfwwgf.

Patented Apr. 17, 1923.

UfN-TIETAEDL ESG PATENT? OIF ALEXANDERE. KEITH, OF HINSDALE, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TO AUTOMATIC ELECTRIC COMPANY, OIF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

TELEPHONE TRUNKING SYSTEM,"

Application led May 21, 1907, Serial No. 374,864. Renewed May 20, 3.918. Serial No. 285,694.v

To all whom it Vmay concern Be it known that I, ALEXANDER E. KEITH, a citizen of the United States ofAmerica, and residento. 'Hinsdale Du Page County, Illinois, have inventeda certainfnew and usetul Improvementin Telephone Trunking- Systems, ofwhich `the followingis aL specilication.

My invention relates to telephone systems o'f that character in `which automatic trunking` is employed 'between calling and; called subscribers. It relates more particularly to systems in which the subscribers linesa-re arranged in groups, and .inwhich the exchange. apparatusis divided and sub-divided ,inw accordance. with" the'size or; capacity `of.Y the exchange. Prior to my invention it has been customary, for example, tok arrange the. subscriberslines inzgroups ot one hundred each, and to provide ten first-selectorsr for each group or" subscribers` 'lines'.y With such arrangement: the subscribers are provided with individual trunlrinfg switches for enabling them to extend? their lines to idle firstLselectorsu In thisuway the tenl first-selectors allottedfto any particular group or subscribers lines are employed' by the subscribers in'thatf group, and are notemployed by the subscribersin any other group. Consequently, if' all` ofthe `:lirst-selectors for. any particular groupof subscribers arev all busy. another subscriber calling from; thesame group cannot obtain an idle first-selector. Furthermore, with this method of. trunlring, the percentage ofi t-runkingr cannotber increasedw-ithout increasing` the number of' first-selectors. For example, in anlexchange inwhich the subscribers are arranged in. groups of one hundredf each, withr ten` firstseleotors for each group, the percentage of trunlring could beincreased by reducing the number of subscribers in each grouptoiifty, mak-ing twice many, groups as before, and by their doubling the number iirst-selec-A tors. With thiserrang rementy the subscribers would be divided. into groups oi fifty, and the number et iirst-selectors wouldvbe twenty per cent of, the total number o'lj subscribers, therefbeingtenv first-selectors for, each group of subscribers.. Evidently, therefore, an increase in the percentage. ot trunlcing with a system. of this kind, wouldv be more or less costly, owing to the increase in the number of selectors, as well as the number of connectors or iinal numerical switches by which the connections are completed directly tothe called subscribers lines.

lVith my improved arrangement, however, the numerical switches, such as first and second selectors and connectors7 are so arrangedy that .they are all common to all of the sub scribers in the diiiierentgroups into which the subst-ations of the system are divided.. In this way there are-no numerical switches whichfarey employed exclusively by certain subscribers, as any` callingsubscriber has access to any and all first-selectors, as well as to any and all second-selectors and connectors. As herein disclosed, I employ nonnumerical trunlring switches between the subscribers individualswitches and the firstselectors, and'in this way each iirst-selector is commonto all-thesubscribers of, the exchange, or at least to-.all ofthelsubscribers of a plurality of the groups into which the system is divided. Such being thecasethe percentage o:t'-trunking can be increased by increasing the number of groups into which the subscribers substationsare divided, and by thus reducingfthe numberl of subscribers in each group` With this'arrangementthere will still be ten trunk lines leading from the individual switches outI eachY group of subscribers,k making ten trunk lines, A for` each titty subscribers, and over` thesetrunk lines the callingsubscribers can connect with any oi the various first-selectors, depending.

upony which oi the first-selectors are busy and which, are idle. It 1s true, of course,

that in-order to increase the trunlring from. `tenl to twenty per cent in the manner Just described, it will be necessary to also increase the number of. non-numerical trunking switches intermediate of the subscribers individualv switches and the iirst-selectors. This, however, willolnf'iouslyl not costy as much as ity would; to double the number of first-selectors, which latter would: be the only method by which the trunlring could be increased trom. tento twenty per cent in the old system. In, fact,y there can be as many first trunlrl lines for each group of subscribers as. there are subscribers in the group, and stillA the number of; first-selectors andsecondfselectors and connectors will.

remain the same, thus increasing the trunkfacilities between the subscribersl telephone lines and the first-selectors, Without necessitating a correspondingl increase in the number of numerical switches. In other Words, with my improved arrangement there could-be ten subscribers in each group, and there could be ten trunk lines leading from the individual switches of each group of subscribers, these trunk lines terminating in the secondary or intermediate non-numerical trunking switches; and with this method of trunking no calling subscriber would ever be delayed for want of a trunk line, and would always get a selector unless all of the numerical switches were in use, which would not be likely to happen. l For practical purposes, however, an increaseof from ten to twenty per cent would ordinarily be found sufficient to preclude any callin. subscriber from being delayed for want of a trunk line leading from his individual switch, as to bring about such a condition in any group of fifty subscribers would require that all ten of the first trunk lines therefor be found busy at the same time, so that the eleventh calling subscriber would find no idle trunk line. Increasing the percentage of trunking to this extent would only require an increase in the number of secondary or intermediate non-numerical switches, and would not'require an increaseV in the number of numeri cal switches. Consequently, as previously stated, my improved method of trunking affords ample opportunity for giving better trunking facilities between the subscribers lines and the numerical switches, without materially increasing the cost of the exchange as a whole.

To the foregoing` and other useful ends, my invention consists in matters hereinafter set forth and claimed.

In the accompanying drawings Figures l 1 and 2 sho-w diagrammatically a portion of a telephone system embodying the principles of my invention. In said figures the calling subscrlbers substation is shown at A and the called subscribers substation atl A. These two substations are shown connected through the medium of automatic switches. As shown, the line of the substation A terminates in an individual line switch C which may be termed a primary non-numerical or individual switch. At D 1s shown a second switch that is common to a number of subscribers stations, such as the substation A, which substations, in the following, will. be considered as belonging to one group. The switch D may be called a secondary' non-numerical trunking switch; It will be understood, of course, that the system may comprise a number of groups of subscribers stations similar to the one to which reference is made. The line switches C .of each of these groups of substations are controlled in this system by a master switch E. yIt is to be further understood that the secondary non-numerical switchesD are also arranged in groups, and that each of said secondary switch groups is controlled by a master switch F. In addition, the system is equipped with selector switches I-I of the general type disclosed in Letters Patent No. 815,321, granted March 13, 1906, to Keith, Erickson it Erickson. These selector switches are also arranged in groups. The exchange is also provided with still further groups of selector switches I which are, more or less, a modified form of the selector switches Il. Thesystem also has connector switches Ii of the general type disclosed in Letters latent No. 815,176, granted March 18, 1906, to Keith, Erickson @t Erickson, but modied to an extent to adapt them to common battery purposes. The line switch C', it will be understood, is, of course, identical with the line switch C. As shown in the various drawings, the system'is provided with a central battery B having its positive terminal preferably grounded at G. This battery is used for both operating and talking purposes.

Figs. 3 and 4, it will be seen, are enlarged and more complete diagrammatic views of the primary and secondary nonlnumerical switches C and D.

Fig. 3 is a detail'view of the master switch bank.

Fig. 5 sho-ws diagrammatically the trunking arrangement used in the system between primary and secondary non-numerical switches, the primary switches being shown in the upper section of the drawing, and the secondary switches being shown in the lower section. In a ten thousand system there will be one hundred groups of primary switches P1, P2, P3, etc., comprising one hundred switches.I C in each group; but there will be only ten groups of second.- ary switches U, V, W, etc., comprising one hundred secondary switches D in each group. The groups of primary switches will extend from left to right, as shown. while the individual unitsor switches will be arranged from front to rear, one hundred deep. The groups of secondary switches will extend from left to right, as indicated, and the units or .switches themselves will extend from front to rear, one hundred deep.

Figs. 6 and 7, taken together, show more particularly the arrangement of the switches. and show in addition the groups of trunk lines leading to the selector switches I-I with reference to the secondary switches U, V, W, etc.

Fig. 8 shows a special wiring arrangement between the primary and .secondary i' switches, whereby if alLl the trunk lines leadingfrom a certain group of secondary switches become busy, allthe masterswitches in the exchange that are retaining their line tizi ,the next set of switches opposite said busy set .of trunk" lines are then caused to operate and advance their allotted liney switches opposite nrunlrv lii z and wl'ierehxv afterwardsall master switches ar? prevented fromy stooping opposite said busy gri-culi of trunk lines until one or more oi` the lines in said group become idle. y Figs. 9. l0, 1l, 12, 13, 14rand are detail views of the impulse-spring mechanism ofthe` subscribers substaticns.

The general method by whichv the central office switching apparatus is operated is as follows: Referring to Figs. 6 and 7, when the subscriber at sub-station A turns the dial for the first digit his individual line switch C is operated by' a preliminary impulse transmitted over the rotary line conductor to seize a trunk line leading to a second line switchlD. As soon'as this second line switch isseizedby the' first line switch it operatesto seize a trunk line` and extend the calling subsc-ribers line conductors to a firstselector switch H. All` these preliminary trunlring operations take place when `the subscriber rotates the dial 'forward for the first digit; but as the dial returns7 theI tirstselector switch is then operated for the first digit. The turning of the dial for the second digit causes the second-selector switch I to select an idle connector-switch K, and

the connector is in turn operated when thedial is turned for the last two digits.

The subs'tations may be of any suitable or approved type, The substation A, in con'- nection with which Ihave elected to illusn trate my invention, comprises a receiver 2, a switch-hook 8 for controlling the substation circuits, which controlling` operations are `accomplished through the medium of any suitable means, such as the cam-arms fh and 6. As Jthe switch-hook is lowered the cam-arm 5 momentarily presses the release` springs 7. 8 and 9 into enga ent.

whereby thesubstation line conductors may be `grounded simultaneously. wWhen the switch-hook is down the cam-arm -t maintains a contact between the springs 10 and 11, therebybridging the ringer 12 in series with the condenser 13 across the line. The substation `ground circuit is normally broken between the ground springs 14 and 15 by the cam-arm 6; but when said springs are together ground potential is provided to the ground postll, and to the release spring T. as `is usually the case in telephones of this type. The said substation comprises the usual transmitter 18, and the induction-coil 19 having the primary winding 20 and the secondary winding 21. Being an automatic substation it is provided with the usual vertical and rotary impulse springs 22 and Oil. The vertical yimpulse spring 22 is providi-zd with an oblique projection, er lu cn the runder side, with which the vertical impulse teeth 25 are adapted to engage for intermittently driving the spring 22 onto the ground post 17. The rotary impulse spring 23 is provided `with yson'iewhat similar mechanism Yfor driving the said rotary .spring onto' the ground post once when the dialis rotated in one direction, and once when rotated in the opposite direction. The said rotary iin-y pulse spring 23 has on its under side all# shaped member 26 having two sides c and el; and there is, in addition, an auxiliary spring 27, which works vin conjunction with said V-shape'd member. As shown more clearly in Fig. 9, the auxiliary spring 27 is provided with a lower curved vpart e havingthe rear section 28 curving outwardly, as showni the vertical impulse teeth 25 approach the', lug 24: of the vertical impulse spring 22,

(Fig. 11), and eventually the first toothA that meets the lug 24 clears the said lug,- as

shown in Fig. 12, but not until after they rotary impulse tooth lclears the curved member e. As `the impulse wheel continues to advance in the direction of thearrow in Fig. 12, the nezrtimpulse tooth will clear the projection 24v., as shown in Then when the impulsey wheel is released, the vertical impulse spring22 is carried into engagement with the ground post 17. `in the manner indicated in Fig. ltglbut as the impulsek wheel. nears its normal position the rotary impulse toothfl passes under the curved member c of the vauXiliary spring 27 (Fig. 1 5), engaging"V the V-shaped nienibe'r V26 directly and for a short time only, sending lthe ordinary impulse through the mediumv oit the rotary impulseA spring 23` to the line, after which the said member 26fis cleared, shown in Fig. 1 0, as the impulse wheel vreaches its normal position. yThe operations as thus described are repeated each time that the dial is operated, and the number of impulses produced through the medium of' the vertical impulse spring 22 is accurately and definitely determined each operation of the dial by the hnger-hole which the subscriber selects on the lt should be stated that a suitable stop is. as is well known in the art, provided to always limit the rotation of the dial, which stop indicates when to release the dial. PS v referring to l. it will `be seen that the impulse springs and are electrically connected with the vertical and rotary line sis ist

llocking dog 34.

locking cam 35 that locks the dog 34 while conductors 31 and 32 that lead to the central ollice. @laid substation is, of course, provided with a dial r(not shown) which is secured to the shaft 33, together with the Furthermore, there is a the receiver is on the switch-hook, to prevent a rotation of the dial. For operating the impulse springs 22 and 23 the substation is provided with the impulse wheel 36 that is secured to the shaft 33, which impulse wheel carries on its periphery the `so-called vertical impulse teeth 25 and one rotary impulse tooth 30, already mentioned. The said impulse teeth are so arranged that when the dial is drawn down the impulse spring 22 is not carried into Contact with the ground post 17 but as the dial returns, first the vertical teeth engage the vertical impulse yspring 22, and after they have completed their work the rotary impulse tooth operates the Vrotary impulse spring 23. ln this operation the subscribers vertical line conductor 31 is iirst given a number of ground impulses, and then therotary line conductor 32 is given one ground impulse.

' It will be seen that as long as the dial is out of normal position the construction is such that the dog 34 permits the primary circuitsprings 37 and 38 to separate, thus preventing thev impulses that are delivered to either line conductor from passing to the other. The means whereby a subscriber may signal a called. subscriber comprises the push-button 39 which, when pressed, carries the spring 40 out of engagement with the Contact point 4 1 and into engagement with the contact point 42, whereby the vertical line conductor 31 is grounded.

The individual or line switch C (Fig. 3)

isof the same general form disclosed in my U. S. Patent No. 1,283,413, granted @ctober 29, 1918. The said switch comprises, as shown in Fig. 3, a plunger 44, plunger arm f 45, bridge-cutoti' relay 46, trip magnet 47 and switch-release magnet 48, Vall of which are built about a switch-base or frame (not shown) or any suitable or approved character. rlhe said switch-release magnet is provided with an armature 49 that is pivoted on a pin 50 which rises from the base of the switch. The said armature carries pivotally secured on its end a second armature 51 that is controlled by the trip magnet 47. The pin 52 about which the armature 51 oscillates is carried on the end of the armature 49. The plunger 44 is pivotally secured bythe pin 53to the plunger arm 45, which latter is in turn pivoted to a pin 54 that rises from the switch-trame, rlfhe lug 55 is stamped or Apressed out ofl the side ot the frame and is provided as a stop or rest for the armature 49.` Upon the armature 5.1 is

secured the catch spring 56 which is adapted to engage the end 57 of the plunger arm into contact in the above-mentioned ordery when the plunger l44 operates.` When the plunger 44 is in locked engagement with the plunger shaft 60, the notch 61 is in engagement with the flange or web of the shaft 60, i

and when in sliding engagement the hub rests in the position shown by the dotted lines in Fig. 3*-that is, when the plunger shaft is operated the plunger 44 is not carried along with the locked plungers, but remains in the dotted'position, the plunger shattsliding upon the end 59. The general operation of the switch is as follows: The trip magnet 47 is energized by a preliminary impulse, and the armature 51 is attracted against the magnet cores. Then the armature 51 is attracted the catch 56 slides out of contact with the end 57 of the plunrer arm 45, and the said plunger arm 45, owing vto A the tension of the spring 58, moves aboutI the pin 54 and thrusts the plunger 44 into the bank terminalQ, shown in Fig. 3; and when the trip magnet again de-energiZes, the trip armature 51 vfalls against the end of the plunger arm 45. when the release magnet 48 becomes energized, whereby the armature 49 is attracted,r

and accordingly the trip armature 51 is moved upwardly until. the catch 56 slidesV over the end 57 then when the release magnet 48 becomes dee-energized' the armature 4 9 returns to normal position and remains at rest against the stop 55. Furthermore, since the plunger arm 45 is now in engagement l with the armature 51, the said plunger arm is also moved about the piny 54, whereby the plunger 44 is removed from the terminal Q. Also, since the plunger shaft has advanced one step, the hub 59 of the plunger 44 comes to rest in the position shown by the dotted line in Fig. 3, in sliding engagement with the plunger shaft 60; and as the said plunger shaft advances each timev an idle trunk is seized, the plunger 44 is not advanced, but remains in this position opposite the The switch is restored trunk terminal from which it has just disengaged, since the slot 61 is not in engage ment with the plunger' shaft 60. After all the trunk lines have been successively seized, and the shaft 69 is released from its last position, said shaft then starts toward starting point or normal position and picks up the plusser 44j when the .saddle of the Said,

Fu'rthermore', a secondrelay 107 which con- `bridge-vcut-ofl relay 46.

released when another'call ismade.` But if,

after lthe plunger is released, and before the shaft 60 returns tor pick up said plungerl the switch C is again operated, the' plunger '44 again engages vthe same terminal "Fun thermore, ythe `pluruyger arm 45 isl provided with an extension orfinfier 100, so that when the lplunger 44 is tripped into abankthe lcontact spring,r 101 is ythen'pressed into en- `sagement with the spring 102,'wher'ehy an eneiigizi,nnf circuit 'is closed through the The cut-olf relay 46 upon energizing 'operates to shiftfthe spring 103 outot engagement "with the spring` 104 and into 'engagement withthe spring,V 105.l '.lhensth'e springr 103is tlfus operated the vsprings 104 and 106 yalso dis engage.

'lThe master switch E, which may be of any suitable or approved type, is provided tor operatingtheplunger shaft 60,y and'tor controlling certain -'circuits'that will be disclosed hereinafter. VIt comprises the followlll ingfthe ratchet wheel`72', which latter is ilesigned for operatingrthe plunger'shatt 60, and a differential relay 7 3 for controlling7 the energizing' circuit'of the'motor Vmagnet 71.

trols the springs 108 and '109 is also provided foifclosing the Yenergizing circuit of the motor magnet 71." l'flhe'masterl switch also has a bank t) comprisingwtwo sets ol individual contacts t -and l) and ytwo common metallic segments'74 and -l.10,"o'ne foreach setof individual contacts. The wiper .75 adapted 4to remain in constant engagement with the bank` G, andto maintainone oit the segments a in electrical connection with the common segment 7 4, and also to maintain one ot'theindividual segments Y) in elec- 'lrical connection with lthecommon segment 110. preferred arrangement of themaster switch bank is shownin Sawhere the individual segments a and` dare separated from their common segments by the insulatiiw strips 111% It willbe noticed that after the wiper passes over the'seg'ments 'from right toylett and engagestlie last segments, then on the next step the i' wiper 75"passes trom the said ycontacts on the extreme left to the contacts on'tlie extreme right, but in passing tromV one extreme position'to the other thehwiper 75 slides on the insulated member 113. l Itwilllbe seen'lbyV referringf vto the drawings that the contactsonthe exdetailszA motor magnet 71 for operat- 'SW Y VolE they switch D is designed to valways remain 'The magnet 99 serves bothas a trip magnet l and T282. It will further be observed that in Fig. the wiper "divided into two" sections by si'iita'ble' insulation, the extreme end being; insulated from the `reiioainder of the wr er, whereby the contacts'b and the con- 70 tacts e are maintained electrically separated. lnl'Fig. y S; however, thewiper 75 'is 'repre-V sented as being composed of two` sepia-rate and distinct wipers. This provision is made in orderthatfthe' individual segments not bebrought vinto contact with the common segments, whereby some interference "with the successful. operations of they master switch might be experienced. The contacts @and Z2 are the termina'ls'of the conductors 0 over which guarding; potentials are provided for operatinathe masterswitch E.y The cntictsma, are allotted to the'trunkdines lea-'ding f n the primary switches to the secondary .en itches, whiley the contacts '6" arev allotted V85 individually toa group of trunk-lines leadingtrom the secondary switches to the lirstselector switches-that is, if all thefirstselectors ot a group are busy simultaneously, a guarding potential appears at ja""contact 6,790 allotted to this group, and the master switch wiper 7 5, in passing over these contacts. produces no'eflect unless there Vis a'guar'ding potential present,` in which 'event the motor magnet is `energized as usual. 95 The mechanical details of the secondary switch D, as well as' the mode of operation, are very much the same as those ofthe primary switch (l. "lt will beseen that' the primary switch C is supplied with a release magnet 4S and a trip magnet 47 and with a cut-off relay 4.6, while the secondary switch `l) is'onlyv equipped'with a magnet l99 that performs not only the functions of a release magnet, but also an additional function 'ch the releasevmagnet 4S ot the primaryl itch (l does not perform. This magjiiet- 99 renensjired during' the operation ot the switch. 1 m

andas a release magnet; forwhen the said magnet is energized the armature 111 is attracted, and the plunger'QT on the arm 98 is in turn thrust into its switch bank. Now, when the magnet deeneifgiizes, the armature then returns to normal position, thereby returning the plunger to` normal position. Thus. through the medium ofthe magnet`99, the plunger is thrust into the bank and then withdrawn. The armature 111 is pivotally u secured to the switch-frame (not shown) at the point 112, and at the other end the link 113 is pivotally secured at the point 114, The connecting link `113 is in turnpivotally se'ciiiediat. the point 115 to the Vplunfiger arm which rotatesabout the point 11G. 'By means of the spring 117 which is'riiieted to the plungenarm 98, thel plunger arm mechanism is restored to normal position. upon the deenergi'zation ot the maggnetQl. lo

llo

The plunger arm 98 is provided with a finger 118 which, when the plunger 'is operated, shifts the spring 119 out of engagement with the spring 120 and into engagement with the spring 121, as shown in Fig. 4. By thisr operation the magnet 99 is disconnected from the conductor 125 which leads to the motor v bank 0 of the master switch F is a single ybank and nota double bank as shown in Fig.

3a. A motor magnet 122 is provided for operating the ratchet wheel 123 which in turn operates the plunger shalt 124. The relay 126 is provided for controlling the energizing circuit oi"` the motor magnet 122. The master switch bank 0 comprises only one set oi' individual contacts and only one com- Amon metallic segment 127. The operation ot the master switch F, cn the whole, is the saine as the operation of the master switch hl, and `the description previously given in connection with the master switch E will be sufficient.

The selector switch H, as already stated, is a modified form of a well-known form oi selector switch. lt is provided with a vertical magnet 128 and a rotary magnet 129, a release magnet 130 and a private `magnet 131. The said private magnet, of course, controls the side switch wipers 132, 133, 134 and 135, and also the circuit of the vertical -Inagnet 128 and release magnet 130, in the usual manner, by means of the springs 136, 137 and 138. rllhe'vertical movement of the switch shaft (not shown), and, therefore, of the wipers 139, 14() and 141, is controlled by the vertical magnet128, and the rotary movement by the rotary magnet 129. ln'cluded in the energizing circuit of the rotary magnet are the usual interrupter springs 142. The operative magnets of the switch are controlled by the subscriber through the medi'um of the vertical and rotary relays `143 and 144, as is well known. Said relays have under their control the usual springs 145,

.146 and 147. By means ot the back-release relay 148 the release or" the switch H is brought about after the side switch has passed to third position.

The selector l is, as already stated, much like the selector H. lt is of the trunk-release type, in which the vertical and rotary line relays 149 and 150, acting conjointly, press the release springs 151 and 152 into contact, the i'ormer of which is connected to the trunk-release conductor and the latter with the release magnet 153, whereby an energizing circuit is closed through the re-A lease magnet 153. The selector l is also pron Vvided with the vertical magnet 154, the rotary magnet 155 and the private magnet 156. Unlike the private magnet of the selector switch H, the private magnet 156l of the selector l does not control the release magnet 153. means whereby' the selector switch may be released after theside switch passes to third position. v

ln the connector switch K the vertical and rotary line relays 158 and'159 may be operated to impart to the shaft wipers 160, 161 and 162 their vertical and rotary motions. l/Vhile the side switch is in first position the vertical line relay 158 controls the vertical magnet 163, and when the side switch passes to second position the rotary magnet 164 comes under the control of the said relay; and similarly when the side switch passes to third position the ringer relay 165 is placed under the cont-rol of the vertical line relay The connector rotary line relay 159, as is well known, controls the private magnet 166, which latter in turn operates to shift the side switch wipers 167, 168, 169 and 170 from iirst to second position and from sec.

ond to third position. The two line relays, acting conjointly, provide means whereby the release magnet 171 may be. energized to release the connector switch. The differential relay 17 2 controls the energizingcircuit oit' the back-bridge relay 173, through which latter the called substation receives battery current for talking purposes. The said relay 173 upon energizing closes a circuit which in turn provides the calling substation with battery current for. talking purposes.

The central oliice is provided with a suitable ringer generator R and a busy-signaling machine M.

A. clearer understanding of the principles ott my invention may be had by following the general operation of the apparatus when one subscriber calls another. Assume` for example, that the subscriber at substation l desires to call the subscriber at substation A Y to which is allotted the line #2220. To call the number 2220 the subscriber at substation A raises his switch-hook and operates the calling device once, in the `well-known manner, for each digit. When the dial is drawn down for the first digit a preliminary impulse is, as already explained, transmitted over the rotary line conductor 32, which preliminary impulse energizes the trip magnet 47, whereby the non-numerical primary line switch C' is operated to seize an idle trunk line leading to a secondary non-numerical line switch D', Vwhich is in turn operated by the primary switch C to seize an idleI The back-release relay 157 provides trunk line leading to a first-selector switch H. The dial, in returning to normal position lfor vthe vlirst digit, operates the iirst-selector switch to establish connection with an idle trunk line leading to a second-selector l. The `second'selector I, in a similar manner,

lis operated ttor thesecond digit to select an idle trunk line leading to a connector switch -'K. It 4will be understood, el course, that when the dial Vis turned for each digit a preliminary impulse is transmitted to the rotary line conductor,- which impulse, it a selector H or I or aconneotorfl is on the line, is re ceived by the rotary line relay or the rswitch `While thevside switch is in iirst position.

This rotary line relay, of course, energizes, but since the side switch is in iirst` position such energizing isl Without effect, and the Y switch is not operated until the dia-l delivers "the vertical impulses. The reason that the erating the side switch ot the selectors preliminary impulses are not eil'ectilfe 1n ep and lor the connector K 1s due to the fact that 1- the side switch is locked in first position unpulse for operating the line switch C, which occurs when the callingsubscriber rotates the dial forward tor the lirst digit, is caused by the rotary impulse spring` 23 being pressed against'the ground post 17. As a result of i thisf impulse the trip magnet l17 oi the line switch C is energized by a flow oit current from ground G to the springs 1li and 15,

ground ypost 17 ,impulse spring 23 to the rotary line conductor 32, conductor 174i, cut-oil' relay springs 104e and 106 to the trip magnet 47, thence through said trip magnet to the conductor 175, springs 17 6d and S7, through the Winding` of the motor magnet 71 to the battery lead 176, thence through battery B to ground G. Although this circuit includes the motor-` magnet 71, this magnet 71 does not operatively energize, since the magnet i7 is ot much higher resistance than the-magnet 71. As soon as the trip magnet i7 energizes, the armature 51 is attracted, and the plunger is'liberated and thrustA into the bank terminal Q by the spring 58, assuming` that the plunger 44; is yopposite the terminal Q. at the time. VvThen the plunger 44 engages the `bank terminal Q an energizing circuit closed through the motor magnet relay 73,' which in 'turn operates to close an energizing circuit through the motor magnet 71. The

motor magnet then operates to advance all,

idle plungers that are in locking engagement tith thefshaft to a position opposite the nent idle bank terminal, similar to the terminal Q. The circuit `through the relay extends from ground G2 through the Winding 177 of the `relay 7 3, segment 7i, Wiper arm 75, segment Sel, conductor 178, l anla terminal springs 7 0 and 69, release magnet le te the battery lead 176, thence through battery l to ground ii. Although this circuit in*-V cludes the release magnet 48, the magnet does not operatively energize, since the Windings of the relay 7 l are of' a high resistance, While the Winding ofthe release magnet is t Set, over tl c following circuit: troni. gizing operates to place the springs 87 and 8S in contact, whereby a circuit yis completed through the motor magnet 7l extending from ground G3 through the springs 88 and 87,

motor magnet springs 85' and 8G, through the motor magnet 71 to the battery lead 170, thence through battery B to ground tgl. The motor magnet 71 upon energizing attra-cts its armature 81, whereby the pavvl 82 engages the ratchet Wheel 72 and rotates the. Wheel one step.

lillhen the armature 81 is attracted against the magnet cores the springs 85 and 86 disengage, thereby breaking the energizing circuit through the motor magnet. The cam being in engagement with the pin 77 is operated to advance the plunger shaft 60 and all idle plungers that may be in normal or locked engagement with the said shaft one step and opposite another trunl; terminal similar to the terminal Q, assuming the next succeeding trunk is idle. Consequently, the wiper 75 is carried from the contact point 84e, which corresponds to the terminal Q, to the Contact point 89, which latter corresponds to the terminal before which the advanced idle plungers are now resting. The

effect olf the movement oi: this wiper 75 over the contacts need not be considered at present- Suppose that nine subscribers have called, and that the master switch has thus been operated nine steps, carrying the wiper 75 to the last Contact point 112, New. when the motor magnet 7l operates for thev next sten--rvhen the tenth subscriber callsthe A 75 passes back and drops into engagement with the Contact point 84:, as already explained, ll? the first trunk is still busy the iviper 7 5 linds liiattery current on Contact 04;, and an energizing circuit is established through the differential relay 75S. which in turn operates to close an energizing circuit throufrh the i'notor magnet 71. The current through the said relay 73 tloivs from the l contar-t Sil through the Wiper 75 to the common segment 711, through the winding 177 o? the differential relay 73 to ground (l2. lllhen the di rential relai.7 73 attracts its ern .ture the differential relay springs 87 and @il are pressed inte contact, thereby clos-` ing an energizing circuit ior the motor magnet 7 1 :from .frennrl G3 tlfrough the said Sil ai, through the motor mag- S5 and 86. motor magnet 71,

. the battery lead 171iy and through:iy

battery 11 to ground (i, lhe motor magnet then operates, as previously expiained, to rotate the ratchet wheel one step tor advancing the plunger shaft one step, and

the master switch bank wiper 75 one step also, into engagement with the second segment 89. The plunger shaft 60, when thus advanced one step, carries aii idle plungers that are in engagement with the said shait to a position opposite the next bank terminal, previously explained. 1t there should still be a guarding potential at the bank segment 89 et the master switch bank the differential relay 73 wiil remain energized, whereby the energizing circuit through the motor magnet is again -completed when the motor magnet springs 85 and 86 again engage; and as a result the motor magnet 71 is again operated, whereby the plunger' shatt 60 and the master switch wiper 7 5 are advanced another step. rilhis process continues as long as the wiper 75 continues to find segments with guarding potentials. As soon as an idle segment is found, however, the energizing circuit through the diii'erential relay 73 is broken, at which time the said relay in turn breaks the energizing circuit ior the motor magnet 71, until the next subscriber makes a call. "At the instant that the plungerI 44 enters the said .bank terminal Q the following springs are pressed into contact: 63 and 64, 65 and`66, 67 and 68, and 69 and 70. Also, the springs 102 and 101 are pressed into contact by the inger 100 on the end of the plunger arm 45, whereby an energizing circuit is closed through the cut-cti relay 46, said circuit extending fr m ground G4 through the springs 192 and 101, through the relay 46 to the battery lead 176, and through battery D to ground Gr. rhe engagement ot' the springs 101 and 102 establishes a guarding potential, by way or the normal conductor 96, to the connector private bank contacts corresponding to the line that terminates in the line switch C, to prevent any subscriber from calling the said line after the calling subscriber at substation A operates his dial preparatory to making a call, as explained. rihecut-oti1 relay 46 upon energizing operates to shift the spring 103 from the springs 104 and 106 and into en# gagement with the spring 105. By this operation the subscribers vertical and rotary line conductors 31 and 82 are disconnected from the trip magnet, and the Vertical normal conductor 94 is connected with the Vertical line conductor 31. The engagement of ythe bank springs 67 and 68 closes an energizing circuit through the trip n'iagnet 99 of the secondary line switch D (Fig. 4), said circuit eXtending from ground G5 through the springs 68 and 67, conductor 98, through the vwinding of the magnet 99, springs 119 and 120, conductor 125, motor magnet relay springs 179 and 180, motor magnet springs potential at the master kswitch bank contact 84, over the 'followings circuit: F rom battery B to the battery lead 176, thence through the release magnet48 and springs 69 and 7 0 over the conductor 178 to the said contact point 84. This guarding potential protects the seized trunk conductors 90, 91, 92 and 98 from being seized by other plung ers, already explained. The closure of connection between the springs 68 and 64 eX- tends the calling subscribers Vertical line conductor 31 to the vertical trunk conductor 90 and to the bank spring 183 of the secondary switch` D. The closure of contact between the springs and 66v in asimilar manner extends the subscribersrotary line conductor 82 to the rotary trunkconductor 91 and to the bank spring 184 of the line switch D. 1t will be understood that the bank terminal being the first bank terminal ot the line switch bank, corresponds to the iirst segment 84 of the master switch bank O' and, therefore, to the trunk line the conductors 90, 91, 92 and 98 of which terminate in the secondary switch D. When the magnet 99 of the line switch D energizes, as explained, the plunger 97 is thrust intothe bank Q and the spring 119 is shifted out or".y

Also, the closure ot connection betweenr the springs 69 and 70 establishes a guarding engagement with the spring 120 `and into engagement with the spring 121, whereby a new energizing circuit isl established through the magnet 99. This circuit extends from ground G5 at the line switch C through the springs 68 and 67, conductor 93, through the magnet 99 and springs 119 and 121 to the battery lead 176, and through `battery B to ground Gr, thus :forming a locking circuit or the said magnet, which circuit is maintained as long as the line switch C `remains in connection with the trunk line conductors 90, 91, 92 and 93. `@t course, as

long as the"`magnet 99 remainsI energized the plunger 97 maintains the bank springs oi the bank Q in contact in the following order: 188 and 185, 184 and 186,187 and 188, and 189 and190. V hen the plunger 97 engages the bank terminal Q an energizing circuit is closed through the'motor magnet relay 126, which `in turn operates to close an energizing circuit through the motor mag net 122. The motor magnety then operates to advance all idle plungers which are in locking engagement with theshaft 124 to a posit-ion opposite the next idle bank terminal, similar to the terminal Q. The circuit through the relay 126 extends from ground G through the winding 191 of the relay l126, conductor 192, segment 127, wiper arm 193, segment 194, conductor 195, through the bank springs 190 and 189, conductor 92, through the bank springs and 69 ofi the switch C, through the trip magnet 48 to the battery lead 176, and through battery B to ground G Although this circuit includes the release magnet 48 said magnet does not operatively energize, since the winding 1.91 of the relay 126 is ot high resistance, while the winding ot the release magnet 48 comparatively low. The relay 126 upon energizing operates in the same manner as the relay 73 or the master switch E to close au energizing circuit through the motor man' net 1 which in turn operates (as explained in connection with the motor magnet 71) to advance the plunger shaft 124 and all engaging or locked plungers one step to a position opposite another trunk terminal similar to the terminal Q', assuming that the next trunk line is idle. Consequently, the wiper 193 is carried from the contact point 194 to the contact point 196. The closure of contact of the springs 183 and 185 extends the calling subscribers vertical line conductor 31 to the trunk conductor 197, and to the side switch wiper 132 ot the first-selector switch H (Fig. 2). The closure ot contact of the springs 184 and 186, in a similar manner, extends the subscribers rotary line conductor 32 to the rotary trunk conductor 198 which leads to the side switch wiper 133 of the selector H. `The subscriber has thus established connection with the first-selector I-Land now when the dial rotates 'back tor the tirst digit the first-selecl tor H is operated. The firstldigit being the spring 22 is pressed onto the ground post 17 twice. As a. result, the vertical line relay 143 ot the tiret-selector H is energized each time by' a iow of current 'from the substation ground G through the springs 14 and 15 to the ground post 17, thence through the spring 22 to the vertical line conductor 31, line switch bank springs 63 and 64, vertical trunk conductor 90, bank springs 183 and 185, conductor 197, side switch wiper of the selector' H, contact point 200, vertical line relay 143 to the battery lead 176, thence through battery B to ground G. Each time that the vertical line relay 143 energizes, the line relay spring 145 is pressed onto the ground spring 146. The vertical magnet 128 is thereby energized, and the wipers 139. 140 and 141 of the selector H are raised to the second bank level, opposite the first contact of said level. The energizing circuit for the said vertical magnet 128 extends from ground G7 through the springsI 146 and 145, private springs 137 and to the vertical magnet 128, thence to the batteryr lead 1.7 6, and through battery B to ground G Thev rotary impulse spring 23 is then pressed onto the ground post 17 once,

grounding the rotary line conductor 32 and energizing, therefore, the rotary line relay 144` ot the selector H. The energizing current passes from ground G to the rotary line conductor 32, thence it flows through the line switch bank springs 65 and 66, rotary trunk conductor 91, bank springs 184 and 186, conductor 198, side switch Wiper 133 ot' the selector H, contact point 201 to the rotary line relay 144, to the battery lead 17 6, and through battery B to ground G, The ro tary line relay 144 upon energizing presses the line relay spring 147 onto the ground spring 146, thereby establishing a circuit through the private magnet 131 from ground G7 through the springs 146 and 147 to the private magnet 131, and through the said magnet to battery lead 176, thence through battery B to ground G. The private magnet upon energizing and cle-energizing permits the selector side switch to pass troni iirst to second position, permitting the side switch wipers 134 and 135 to engage the contact points 202 and 203, respectively. The closure or' connection between the side switch wiper 134 and the contact point 202 sets up an energizing circuit for the rotary magnet 129 from ground GS to the contact point 202, through the side switch wiper interrupter springs 142, rotary magnet 129 to the battery lead 176, and thence through battery B to ground G. The said rotary magnet 129 then operates to rotate the wipers 139, 140 and 141 of the selector H into engagement with the first contacts of the second level of the selector H, Jfrom which' contacts it is assumed that the trunk line conductors 204, 205 and 206 lead to the second-selector I. It the first trunk is busy, however, and the wipers have to pass over busy trunk lines, then as soon as the private wiper 141 engages the lirst grounded privatebank contact point, the private magnet 131 again energizes, locking the side switch in sec-ond position. The energizing circuit Jfor said private magnet extends from the grounded terminal G of battery B through an occupying switch (not shown) to the private wiper 141, thence over the conductor 207 and through the back-release relay 148 to the side switch wiper 135, cony tact point 203, private magnet 131, thence through said magnet to the battery lead 176, and through ybattery B to ground G.v The private magnet 131, when thus energized, locks the side switch in second position and the wiper 134 in engagement with the contact point 202, whereby the rotary magnet 129 will be energized step by step until the wipers are carried beyond the lastbusy trunk line. At the instant that the private wiper leaves the last busy contact point the energizing circuit through the private magnet 131 destroyed, and as a result the selector side switch passes to third wipers' 132 and 133 engage the contact points 208 and 209, respectively. Not only is the subscribersline thus extended, but a guardi: ing', potential is established at the private wiper 141, when the side switch wiper 135 passes onto the'ground contact point 210, for protecting the seized trunk line against interference by other calling' subscribers. This guarding potential is established from ground G9 to the contact point 210, 'thence through the side switch wiper 135 and through the back-release relay 148, conductor 207 tothe private wiper 141. 1t will he seen,

. of course, that the energizing circuit for the rotary magnet 129, to which reference has already been made, is destroyed when the idle trunk line is seized-that is, when' the side switch wiper 134 leaves the contact point 202.

The second digit of the called number being 2 the calling subscriber again Operates his dial accordingly, as a result grounding the vertical line conductor 31 when the spring 22 meets the ground post 17. The vertical line relay 149 ofthe switch l. is, therefore, energized twice by a flow of current 'fromthe substation ground G to the vertical line conductor 31, thence through the line switch bank springs 63 and 64 to the vertical trunk conductors and 197, thence to the side switch wiper 132 of the selector H, contact point 208, vertical line shaft wiper 139, vertical trunk conductor 204, side switch wiper 211, vertical line relay 149 to the battery lead 176, thence through battery B to ground Gr. That is, when the vertical line conductor 31 is grounded for the second digit an energizingcircuit is established through the vertical magnet 154 which operates to carry the shaft wipers 212, 213 and 268 step-by-step to a position opposite the bank terminals of the second level. lVhen the rotary line conductor 32 is grounded after the vertical. impulses the rotary line relay 150 is energized, whereby an energizing circuit is established through the private magnet 156, which in turn operates to release the side switch as described in connection with the selector H;

Nhen the switch I comes to rest it is assumed that the shaft Wipers 212 and 213 stop in engagement with the trunk conductors 214 and 215, respectively, as shown,

whereby the calling subscriber-s line conductors 31 and 32 are extended to the connector switch K. The ground impulses from the substation to the line conductors for the last two digitswnamely the third and fourth-f are effective in operating the connector K.

The third digit is called after the subscriber has established connection with the connector K by wayot the trunk conductors 214 and 215. The subscriber rotates the dial, as described, for the third digit 2, thereby grounding` the vertical and rotary line conductors 31 and 32, which causes the energization of the connector vertical and rotary line relays 158 and 159, and also olf' the diiierential relay 172. The energizing); current Hows over the iliollcwiug path: 'troni ground lr to the vertical line conductor 31, trunk conductors 90, 197, 204 and 214, through the winding of the vertical line relay 158 and winding 216 of the differential coil 172 to the battery lead 176, thence through battery B to ground'G. Each time the vertical line relay 158 is energized the .line relay springs 217 and 218 are pressed into contact, and an energizing circuit is established each time through the vertical magnet 163. The energizing of the differential relay 172 is of no consequence at this time. The energizing current through the vertical magnet 163 flows `from ground G10 to the springs 217 and 218, private magnet Asprings 219 and 220, side switch wiper 169 to the vertical magnet 163, to the battery lead 176, thence through battery B to ground G. Each time that the vertical magnet 163 is energized it raises the shaft and wipers 160, 161 and 162 one step at a time until the said wipers are carried two steps and brought Opposite the level in which are located the terminals of the line #2220. lVhen the rotary line conductor 32 is grounded the rotary line relay 1539 and differential relay 172 become energized through the following path: trom ground i to the 'rotary line conductor 32, trunk conductors 91, 198, 205 and 215, through the winding ot' the rotary line relay 159 and winding 221 ot' the differential relay 172 to the baclcbridge relay springs 222 and 223, which are normally in contact, to the battery lead 176, thence through battery` B to ground G. The energization of the rotary line relay 159 causes the springs 224 and 217 to come into Contact, thereby completing a circuit through the private magnet 166. The path of the energizing circuit is from ground G10, linerelay springs 217 and 224,

through the winding of the private magnet 166 to the bach-bridge relay springs 222 and 223, to the battery lead 176, thence through battery B to ground G. The momentary energization of the private magnet 166 causes the release oit' the side switch from first to second position, thus placing the side switch wipers 169 and 170 in contact with the points 225 and 226, respectively.

The last digit being naught, the subscriber operates the dial as previously described, grounding the vertical line conductor 31 ten times and the rotary line conductor 32 once. The vertical and rotary line relays 158 and 159 are operated over the reviously traced circuits. However. when the line relay springs 217 and 218 engage, a circuit is then closed through the rotary magnet 164, instead ot through the vertical magnet 163. The circuit may be traced trom ground G to the 'line relay springs 217 and 218, side switch wiper 169, contact point 225, through the rotary magnet 164 to the battery lead 176, thence through battery 13 to ground (l. Ear-h time that the rotary magnet is energized the rotary armature is attraftcd and rotates the shaft carrying the wipers 160. 161 and 162 one step at a time until the said wipers are carried into engagement with the normal conductors 227, 228 and 229, the tirst two of whic-h lead `to the line ot the desired subscriber, whose number is 2220. The energization of the rotary line relay 159 ttor the last digit completes au energizing circuit through the private magnet 166 which now operates with one ot two results, namely the release oi' the side switch from second to third position, or the so-calledv busy-release o'l the Connector it the called line is busy. Suppose the lormer result to occur and the side switch to pass to third position, 'thus placing the side switch wipers 167. 168, 169 and 170 in Contact with the points 230, and 233, respectively. When the side switch wiper 169 engages the contact point 232 the ringer relay| 165 comes under the control oi" the vertical line relay 158 in the same manner in which the rotary magnet 164 comes under the control oit the vertical line relay when the side switch passes from first to second position. Furthermore, when the side switch passes to third position a. guarding potential is established tor the protection ot the called line. This guarding potential extends from ground G11 to the side switch wiper 170, thence to the shat't wiper 162 that now engages the private contact ot the called line. The said guarding potential at the private wiper 162, furthermore, causes a flow of current to be sent through the bridge-cutoff relay 234 from the said private wiper 162 to the private normal conductor 229, to the bridge-cut-otf relay 234, thence to the battery lead 176, and through battery B to ground G. The said relay upon energizing operates to carry the spring out oit engagement with the spring 236 and into engagement with the sprin 287. .Vhen the spring 235 leaves the Spring the springs L36 and 288 also disengage, thus disthe inst' connecting both the vertical and rotary line conductors 239 and 240 ot the called substation from the trip magnet 241 ot the line switch C. Then the spring engages the spring 287 the vertical normal conductor 227 is extended to the vertical line conductor To signalthe called subscriber the calling subscriber presses the signaling button 39, placing the spring in contact with the substation ground G and thereby energizing the vertical line relay 158 from ground G through the springs 14 and 15, contact point 42, spring 49, springs 37 and 88 to the vertical line conductor 31, thence over a. path previously traced. lhen the vertical line relay 158 becomes energized the differential relay 172 is also energized through the vwinding 216. The armature is attracted and thc sprinf-r 242 and 243 are placed in contact, thereby completing the energizing circuit through the ringer relay 165, said circuit extending from ground G10 through the springs 217 and 218, private magnet springs 219 and 220, side switch wiper 169, contact point 232, through the ringer relay 16T, diii'erential relay springs 243 and 242 to the battery lead 176, thence through battery B to ground G; and as a result the ringer relay becomes energized forcing the. springs 244 and 245 into contact with the ringer generator springs 246 and 247, respectively. As a result, ringing current is permitted to pass out on the line ot the called subscriber, which current passes tlni'ough the substation ringer 248 and signals the subscriber. This signaling current passes from the generator R to the springs 246 and 244, side switch wiper 167, contact point 230, shaft wiper 160, normal conductor 227, springs 237 and 235, vertical line conductor 239, condenser 249, ringer 248, springs 250 and 251 to the rotary line conductor 240, normal conductor 228, shaft wiper 161. contact point 231, side switch viper 168, ringer relay springs 245 and 247 and back to the generator R. As soon as the calling subscriber releases his signaling button 89 the current through the vertical line relay 158 and differential rela-y 172 is interrupted, cle-energizing the said relays.. whereby the ringer relay returns to normal position. As the called subscriber removes his receiver 252 from the switchhook 2:13, the latter upon rising destroys the ringing circuit through the bells 248 at nt the springs 25() and 251 separate. rThe switch-hook also forces the primary circuit springs 254 and 255 into contact, closing a` circuit through its own station that provides the transmitter 256 and the primarxf winding` 257 oi the induction-coil 258 with current for talking purposes. The current `for this circuit passes Jfrom ground 

